The objective of the proposed project is to provide an empirically-based understanding of preschool oral language and preliteracy skill development in children from Spanish-speaking families. The language skills that children from Spanish-speaking homes present at school entry are highly variable and poorly understood. The knowledge base regarding the processes and outcomes of dual language development is inadequate either to design maximally effective educational programs or to match children to the programs they need. There is currently more information available on dual language learners in school than on the factors that shape their readiness for school. The method of the proposed project is a 2 1/2- year longitudinal study of 120 children in the U.S. who have one or two native Spanish-speaking parents and a control group of 60 monolingual English-learning children. At 6-month intervals from the age of 2 1/2 to 5 years, detailed assessments will be made of properties of the children's environments and their language experiences inside and outside the home. In the first year, assessments will be made of the quantity and quality of caregivers' child-directed speech (in both languages for the dual language learners) based on videorecorded caregiver-child interaction. At each assessment point, the children's receptive and expressive speech and language skills (in both languages for the dual language learners) will be assessed using standardized tests, investigator-developed instruments, and spontaneous speech samples. The specific aims of the analyses are (1) to describe and predict trajectories of speech and language development in Spanish-English dual language learners and monolingual English learners from 2 1/2 to 5 years, (2) to identify, among dual language learners, predictors of successful bilingual proficiency at ages 4 and 5 and indicators of risk for low levels of dual language achievement, and (3) to predict preliteracy skills in dual language learners at age 5 years. The large and growing number of children in the U.S. who live in Spanish-speaking homes makes their academic achievement a public health concern. An estimated 35 million households in the U.S. speak Spanish, and many children who hear a language other than English at home reach school age with low levels of English language skills. The cost of educating children with limited English proficiency is as much as 90% greater than the average cost per child. Despite that expenditure, children with limited English skills are statistically at risk for low academic achievement and its many attendant negative consequences. Efforts to improve these outcomes are hampered by the currently poor scientific understanding of the process of early dual language development. The results of the proposed research will provide a scientific foundation for programs and practices to support the school readiness and ultimate academic success of a substantial portion of the nation's children.